Electric actuator for drive apparatus

ABSTRACT

An electric actuator for use with a variable drive apparatus is disclosed herein. The electric actuator has a rotary design incorporating a magnetic field sensor chip disposed on a circuit board to sense the rotational orientation of the magnetic field of a cylindrical diametric magnet positioned on the end of a control shaft of a hydrostatic drive unit. The circuit board includes a microprocessor, electric motor power control and CAN Bus communication capability. The gear housing of the electric actuator features an integral end cap to accommodate mounting of the electric motor to enable a compact design.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional App. No. 62/543,030 filed on Aug. 9, 2017 and U.S. Provisional App. No. 62/481,422 filed on Apr. 4, 2017. Both of these prior applications are incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

This application relates to a control mechanism for a variable drive apparatus generally, and in particular to an electric actuator for a variable drive apparatus having a rotatable control shaft, the combination intended for use in a vehicle or other mobile power equipment.

SUMMARY OF THE INVENTION

An electric actuator for use with a drive apparatus is disclosed herein. The electric actuator has a rotary design incorporating a magnetic field sensor chip disposed on a circuit board to sense the rotational orientation of a cylindrical diametric magnet positioned on the end of a control shaft of a hydrostatic drive unit. Specifically, the longitudinal axis of the magnet is collinear with the rotational axis of a control shaft of the swash plate of an axial piston variable displacement pump of the hydrostatic drive unit and the longitudinal axis of the magnet is oriented perpendicular to the magnetic field sensor chip.

The electric circuit of the circuit board also includes a microprocessor and CAN Bus communication capability. An electric motor of the electric actuator drives a reduction gear train to rotate the control shaft in both forward and reverse (clockwise and counterclockwise arc). The electric motor output shaft includes an integrally formed worm to drive the reduction gear train. The gear housing of the electric actuator features an integral end cap to accommodate mounting of the electric motor, including mounting of a brush card having attached brushes of the electric motor, to enable a compact design. The integral end cap also facilitates wire routing for improved protection of power conductors. The power conductor wiring is immediately routed (with minimal conductor exposure) into an electrical housing mounted on the gear housing. Power conductors are then routed to the circuit board for microprocessor-enabled power control and from the circuit board to a pair of sealed terminals that protrude through the electrical housing to facilitate connection of external power leads to provide power to the electric motor. A CAN Bus connector is located on the electrical housing in close proximity to the power terminals for efficient routing of vehicle or other mobile power equipment wiring.

The foregoing summary is exemplary of the description only, and a better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth illustrative embodiments that are indicative of the various ways in which the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an electric actuator applied to a hydrostatic transaxle forming a representative drive assembly.

FIG. 2 is a partially exploded view of the assembly shown in FIG. 1.

FIG. 3 is a partially exploded view of a swash plate assembly and the electric actuator of the drive assembly shown in FIG. 1.

FIG. 4 is an exploded view of the swash plate assembly shown in FIG. 3.

FIG. 5 is a partially exploded view of the engagement end of the swash plate assembly and the electric actuator shown in FIG. 3, with the gear housing removed for clarity.

FIG. 6 is an exploded view of the electrical module and additional selected components shown in FIG. 5.

FIG. 7 is a partially exploded view of the drive module and the electrical module of the electric actuator shown in FIG. 2.

FIG. 8 is an exploded view of the gear housing, jack shaft, electrical housing and circuit board rotated 90 degrees in relation to the view illustrated in FIG. 7.

FIG. 9 is an interior elevational view of the transaxle of FIG. 1, from the axle side of the transaxle, with the main housing component removed to show the interior components of the transaxle.

FIG. 10 is a schematic view of a zero turn vehicle incorporating a pair of representative drive assemblies, each including an electric actuator of the present disclosure.

FIG. 11 is a schematic view of a representative drive assembly and additional selected components, including a CAN Bus, of the vehicle of FIG. 10.

FIG. 12 is a partially exploded perspective view depicting an electric actuator of the present disclosure and adaptive components for mounting the electric actuator on a hydraulic pump to form an electric actuator controlled pump assembly.

FIG. 13 is a schematic view of a zero turn vehicle incorporating a pair of the pump assemblies of FIG. 12.

FIG. 14 is a partially exploded perspective view depicting an electric actuator of the present disclosure and alternative adaptive components for mounting the electric actuator on a hydraulic pump to form an electric actuator controlled pump assembly.

FIG. 15 is a perspective view of a mounting adapter shown in FIG. 14, rotated 180 degrees to show its opposite side.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies one or more embodiments of the invention in accordance with its principles. This description is not provided to limit the inventions to the embodiment(s) described herein, but rather to explain and teach the principles of the invention in order to enable one of ordinary skill in the art to understand these principles and, with that understanding, be able to apply them to practice not only the embodiment(s) described herein, but also any other embodiment that may come to mind in accordance with these principles. The scope of the invention is intended to cover all such embodiments that may fall within the scope of the appended claims, either literally or under the doctrine of equivalents.

Additionally, the drawings set forth herein are not necessarily drawn to scale, and in some instances proportions may have been exaggerated to more clearly depict certain features. Also, terms such as “left hand” and “right hand” may be used for convenience to describe orientation of objects as illustrated, but are not to be construed as limiting. It should be noted that in the description and drawings of vehicles disclosed herein, such as vehicle 190 and vehicle 290, like or substantially similar elements may be labeled with the same reference numerals. Or, these elements may be labeled with differing numbers or serial numbers using different prefixes in cases where such labeling facilitates a more clear description or understanding. As stated above, this specification is intended to be taken as a whole and interpreted in accordance with the principles of the invention as taught herein and understood by one of ordinary skill in the art.

FIGS. 1 and 2 depict an electric actuator assembly 30 applied to a representative drive apparatus 20, which is useful in powering a vehicle or other mobile power equipment, and may be referred to herein as a transaxle. Except as described herein, the internal structure and operation of transaxle 20 can be substantially identical to that shown and described in commonly-owned U.S. Pat. No. 7,134,276, the terms of which are incorporated herein by reference in their entirety. Transaxle 20 comprises a main housing 17 and a side housing 18 secured by fasteners 19. FIG. 9 is an interior view showing side housing 18, and in particular, showing the internal structure of transaxle 20, including hydraulic pump 21 rotatably disposed on center section 75 in main sump chamber 69 and controlled by swash plate 29 of swash plate assembly 10. Swash plate assembly 10 is shown most clearly in FIGS. 3 and 4. Hydraulic motor 94 is similarly disposed in main sump chamber 69 and drives motor output shaft 77, which in turn powers reduction gear train 78 to provide motive force to output axle 79. Pump input shaft 74 provides motive force to pump 21 and may also drive an optional charge pump 76. Swash plate 29 is used to vary the output of pump 21. Other typical items include input pulley 22 having a fan 14 mounted therewith, and a bypass arm 16 for placing the hydraulic system of transaxle 20 into a bypass state. A brake arm 15 is provided for actuating an internal brake 23 and an optional charge pump 76 is depicted as being external, and it would be connected to the hydraulic system by known means. The description of the transaxle 20 should be understood to be exemplary only and the features shown therein are not required except as specified in the claims.

FIGS. 1-3 and 5-8 depict different aspects of electric actuator assembly 30, showing it both connected to the transaxle 20 and separated therefrom. Electric actuator assembly 30 is capable of making precise control adjustments to variable drive apparatuses, such as variable displacement pump 21. While variable displacement pump 21 is illustrated as an axial piston pump of the type disclosed in commonly-owned U.S. Pat. No. 6,332,393, it is to be understood that electric actuator assembly 30 may be applied to actuate any drive apparatus having a rotatable control shaft, e.g. hydrostatic transmissions or transaxles of the types illustrated in commonly-owned U.S. Pat. Nos. 6,122,996 and 6,775,976. Electric actuator assembly 30 is similar in some aspects to the electric actuator disclosed in commonly-owned U.S. Pat. No. 9,114,798. All commonly-owned patents cited within this specification are incorporated herein by reference in their entirety. Application of the electric actuator disclosed herein to other types of variable drive apparatuses having rotatable control shafts, such as toroidal, friction and mechanical drives, is also contemplated within the scope of the invention described herein.

Actuator assembly 30 comprises a motor control module 30 a and a drive module 30 b. Motor control module 30 a is shown in exploded format in FIGS. 6-8, and comprises actuator housing 32 having housing cover 38 secured thereto by means of fastener 36 and mounting boss 32 i on actuator housing 32. Motor control module 30 a (including actuator housing 32) is secured to gear housing 31 by means of a plurality of fasteners 35 connected to mounting bosses 31 i, and alignment pins 32 e cooperate with alignment openings 31 j to assist in proper alignment and assembly. Alignment pins 32 e may be integrally formed, as shown, or may be separate components. Actuator housing 32 could also be referred to as a circuit board housing or electrical housing, as it does not contain all elements of the actuator, as will be described in detail herein.

In the depicted embodiment, electric actuator assembly 30 is attached to main housing 17 by means of a mounting fastener 25 attached to lockdown bore 17 a, and pilot 17 b is used for proper alignment of gear housing 31 on main housing 17. In another embodiment (not shown), lockdown bore 17 a can be used as a standard threaded hole in the housing 17 for mounting a portion of a return to neutral mechanism, so the embodiment disclosed herein does not require a significant reconfiguration of an existing housing design. A pair of centering and anti-rotation tabs 31 a is provided on gear housing 31, and located on a horizontal plane through the rotational axis 29Ax of swash plate 29. Anti-rotation tabs 31 a ensure an easy slip-fit of actuator assembly 30 onto pilot 17 b and prevent binding and possible cross-threading when mounting fastener 25 is tightened to secure actuator assembly 30 to main housing 17. Gasket seal 37 and seal land 17 c are provided for proper sealing of the assembled unit.

As can be seen in, e.g., FIGS. 5 and 8, and described in more detail below, fastener 25 serves multiple purposes, including its function as a jack shaft for pinion gear 52. Fastener 25 may also be referred to as a jack shaft or a “shaft/fastener.” Shaft/fastener 25 comprises a first end having a threaded portion 25 a, and a second end having a worm and pinion gear support portion 25 b, along with an integral pinion gear thrust washer 25 c which acts as a bearing surface for pinion gear 52. The integral thrust washer 25 c also serves as a flange that bears against the gear housing 31 when electric actuator assembly 30 is attached to main housing 17. The support portion 25 b extends through and is supported in part by support bore 32 a of actuator housing 32. The second end of shaft/fastener 25 also includes an installation driver interface or recess 25 d for securing the shaft/fastener 25. By performing multiple functions, shaft/fastener 25 reduces costs and improves ease of assembly. An access hole 38 a in cover 38 allows access to shaft/fastener 25 for easy assembly, and this single fastener attachment configuration also enables fast, easy removal of actuator assembly 30 for service. An elastomeric plug 26 can be used to seal the access hole 38 a.

Circuit board 60 is disposed inside actuator housing 32, as shown in e.g., FIGS. 6-8, and comprises a magnetic field sensor chip 46, power terminals 61 for external conductor attachment, and power terminals 62 for internal attachment of electric motor power conductors 40 a. A wire protector or routing clip 39 is depicted for the support, sealing and protection of conductors 40 a. Power terminals 61 extend through power terminal support openings 32 g formed in actuator housing 32 when the unit is assembled and power terminals 61 are sealed in the support openings 32 g. An external partition 32 f is provided to ensure separation of electrical connections when external electrical conductors are attached to the power terminals 61. Circuit board 60 provides CAN Bus capability to actuator assembly 30 by means of, among other things, electrical connector 45 mounted in opening 32 h in actuator housing 32. It will be understood that the specific detailed wiring components of circuit board 60, connector 45 and other components are not depicted in these figures for clarity. One of ordinary skill in the art will understand the appropriate wiring requirements for the embodiment as depicted.

Circuit board support structures 32 k are provided in actuator housing 32, and alignment pins 32 j mate with openings 60 a on circuit board 60 for proper mounting and alignment, particularly alignment of the magnetic field sensor chip 46 with magnet 13 of swash plate assembly 10. A thermal pad 49 is also disposed inside actuator housing 32 between circuit board 60 and cover 38, and a pressure applicator 38 b is formed on cover 38 to apply pressure to the preferably putty-like, thermally conductive thermal pad 49.

As noted above, swash plate assembly 10 comprises a swash plate 29, which may be referred to as a trunnion mounted swash plate, and a drive adapter 11 secured to control shaft 29 b of swash plate 29 by means of a specialized fastener 12. Swash plate 29 includes a pair of trunnions 29 a on opposite sides thereof and rotates about rotational axis 29Ax. A first trunnion 29 a is mounted in a known rotatable manner in a support (not shown) in side housing 18. A second trunnion 29 a has a control shaft 29 b extending therefrom with a mounting interface 29 c formed on the end thereof for engaging a mounting interface 11 c of adapter 11. Control shaft 29 b has a distal end adjacent to the second trunnion 29 a and disposed inside main sump chamber 69, and a proximal end disposed outside of main housing 17. Fastener 12 extends through the drive adapter 11 and engages threaded bore 29 d. The head of fastener 12 includes bore 12 a for receiving and securing a magnet 13, which includes north and south poles 13N, 13S as depicted. After assembly, magnet 13 extends through magnet access opening 32 b in actuator housing 32 to place the magnet 13 adjacent to the magnetic field sensor chip 46 on circuit board 60. The location of magnet 13 as a component of swash plate assembly 10 enables accurate measurement of the true swash plate position, as the longitudinal axis of magnet 13 is collinear with the rotational axis 29Ax of swash plate 29, and is oriented perpendicular to the magnetic field sensor chip 46.

As a further benefit, the mounting of drive adapter 11 directly on swash plate 29 allows the transaxle 20 to be built in a first location and the actuator 30 to be assembled in a second, different location, and then easily connected together. A true neutral position or neutral dead band for actuator 30 may be calibrated using a method similar to that taught in U.S. Pat. No. 9,114,798, which is incorporated herein by reference in its entirety.

Various components of drive module 30 b are shown in FIGS. 5 and 9. Electric motor 40 has a motor housing 28 and a motor shaft 40 b supported by a set of bearings 43, one of which is shown, one of which is mounted in end cap 33, and bushing 42. A bearing support 31 f is shown in gear housing 31 and bushing 42 is also supported in gear housing 31. Motor 40 uses worm drive 55 for providing output to swash plate assembly 10 and more specifically, integral worm 41 is formed on motor shaft 40 b and is engaged to and drives worm gear 51. Worm gear running surfaces 31 c and 32 c are provided on gear housing 31 and actuator housing 32, respectively. Gear train 50 is mounted in gear housing 31 and further comprises pinion gear 52 driven by worm gear 51. Sector gear 59 is engaged to and driven by pinion gear 52, and thus controls the rotational position of swash plate 29. Sector gear running surfaces 31 b and 32 d are provided on gear housing 31 and actuator housing 32, respectively. As noted before, pinion gear 52 is supported on shaft/fastener 25, which also acts to secure actuator assembly 30 to housing 17.

As shown in, e.g., FIG. 5, drive adapter 11 also includes a plurality of projections 11 a for engaging engagement slots 59 a of sector gear 59, as well as a clocked alignment projection 11 b for engaging alignment slot 59 b of sector gear 59, for ensuring proper alignment of the components during assembly. Projections 11 a, 11 b are ramp structures that cooperate with corresponding ramped engagement slots 59 a, 59 b to move sector gear 59 from an approximate initial assembled position into its exact operating position when actuator assembly 30 is attached to transaxle 20. Gear housing 31 includes assembly supports 31 k to locate sector gear 52 in its approximate initial assembled position, but there is no contact with supports 31 k after sector gear 59 is moved into its exact operating position.

Motor 40 is preferably a brushed DC motor, as shown. In addition to motor housing 28, motor 40 comprises end cap 33, power conductors 40 a, grommets 44, and a pair of brushes 72 attached to a brush card 70. A benefit of this design is that brushes 72 are located at the front of motor 40, i.e., adjacent the output end of motor shaft 40 b as opposed to being at the rear of motor 40. Motor 40 is secured to integral motor end cap 31 d of gear housing 31 by means of fasteners 34 which are installed through (and secure) end cap 33 and are attached to threaded openings 31 h formed in end cap 31 d. Fasteners 71 are used to secure brush card 70 to threaded openings 31 g prior to mounting the bulk of motor 40 on end cap 31 d. An O-ring groove 31 e is provided for sealing the unit. Wire routing openings 70 a are formed in brush card 70 for routing power conductors 40 a to grommets 44 (and then through wire protector 39 to power terminals 62). This location of wire routing openings 70 a reduces the size and complexity of the wiring needed, since the wiring exits the motor housing 28 and directly enters actuator housing 32. Furthermore, the use of end cap 31 d of gear housing 31 as a portion of the motor housing, as opposed to having a separate end cap, reduces size and material costs, and improves tolerances during assembly by machining at least a portion of the support structure for worm drive 55 and jack shaft 25 within a single gear housing 31 and thereby ensuring proper gear alignment and gear mesh.

FIG. 10 depicts a zero turn vehicle 190 incorporating an embodiment of a vehicle control system 180. Vehicle 190 includes a frame 192 on which is mounted a prime mover, such as internal combustion engine 191, that drives a pair of hydrostatic transaxles 194L, 194R by means of a conventional power transfer apparatus, such as belt and pulley system 197. Internal combustion engine 191 may further drive (by means of belt and pulley system 197) an optional mowing deck 198 having mowing blade(s) 198 a. Mowing deck 198 may be selectively engaged by operation of a manual or electric clutch-brake-pulley mechanism (not shown). Transaxle 194L is essentially the same as transaxle 20 described previously herein and transaxle 194R is essentially a mirror image of transaxle 20, 194L.

Each of the hydrostatic transaxles 194L, 194R includes an output axle 179 engaged to a drive wheel 193 to provide propulsion and steering as directed by the vehicle operator via control levers 183L, 183R engaged to respective speed control mechanisms 165L, 165R or via an optional joystick 199. For purposes of this disclosure, the respective speed control mechanisms 165L, 165R may include any or all of the speed control mechanisms, features and functionality described in commonly owned U.S. patent application Ser. No. 15/377,706, filed Dec. 13, 2016, which is incorporated herein by reference in its entirety. Vehicle 190 also has a pair of non-driven, non-steered caster wheels 195 that freely pivot and track in response to the steering impetus provided by the drive wheels 193. Each hydrostatic transaxle 194L, 194R has an electric actuator 130L, 130R mounted thereon to control the output thereof. Electric actuator 130L is essentially the same as electric actuator 30 described previously herein and electric actuator 130R is essentially a mirror image of electric actuator 30, 130L. Electric actuators 130L, 130R receive power from a 12V battery 175 that is charged by an alternator or similar power generating device (not shown). Each electric actuator 130L, 130R is connected to a Vehicle Integration Module (VIM) 161 by way of a CAN Bus (communication network) 160. CAN Bus 160 is powered through the VIM 161, which receives power from battery 175 when key switch 162 is turned on, and directs power and serial communication through CAN Bus 160. The aforementioned pair of speed control mechanisms 165L, 165R (each comprising an optional neutral switch 166 and a speed and direction controller 167) are also in communication with the VIM 161 via CAN Bus 160. Control signals are generated and transmitted via CAN Bus 160 in response to operator manipulation of the left and right-side control levers 183L, 183R engaged to the pair of speed control mechanisms 165L, 165R. A CAN Bus termination 168 (comprising a resistor) is connected to each end of the CAN Bus 160 network wiring harness to ensure communication speed and signal integrity on CAN Bus 160. This type of termination is necessary and typical in a CAN Bus communication system.

Vehicle control system 180 comprises a number of intelligent, electronic modules functioning as a single system and coordinating their activities via CAN Bus 160. These modules include (but are not limited to) the aforementioned Vehicle Integration Module (VIM) 161; Lap Bar Sensor Modules (LBSM) 165L, 165R (also referred to herein as speed control mechanisms 165L, 165R); Joystick Control Module (JSM) 199 (also referred to herein as joystick 199); High Speed Actuators with integrated Electronic Drive Modules (HSA-EDM) 130L, 130R (also referred to herein as electric actuators 130L, 130R); CAN Bus Termination Modules (CTRM) 168 (also referred to herein as CAN Bus terminations 168); User Interface Module (UIM) 163; Diagnostic Module and graphical user interface or GUI (DIAG) 164; and Stability Control Module (SCM) 181. Additional information regarding such modules may be found in commonly owned and currently pending U.S. patent application Ser. No. 15/640,300, the terms of which are incorporated herein by reference in their entirety.

Operator Commands (in the form of absolute position data) are generated by the LBSM 165L, 165R and/or JSM 199 modules and communicated to the CAN Bus 160 network.

The HSA-EDM 130L, 130R and VIM 161 may be configured to monitor these commands and, if valid, respond by driving the actuator(s) to the requested position(s). Invalid commands are responded to with appropriate error handling or failsafe routines.

The VIM 161 monitors vehicle status and overrides operator position commands if necessary for proper control of vehicle 190. The VIM 161 may provide status information to the operator of vehicle 190 for a variety of system functions including speed, operating temperature and battery status when the vehicle contains a UIM 163 and this feature is enabled.

The HSA-EDM 130L, 130R system will continuously compare the actual actuator positions to the operator-requested positions and drive the actuator motors to the commanded positions using a motion profile based on tunable parameters stored in the non-volatile memory of each HSA-EDM 130L, 130R.

The UIM 163 displays vehicle status information messages generated by the VIM 161 and transmitted via the CAN Bus 160 to the vehicle operator.

The SCM 181 can process signals generated by an Inertial Measurement Unit (IMU) to modify operator drive and steering command signals sent to the electric actuators 130L, 130R. The IMU component may comprise a gyroscope, accelerometer and magnetometer. SCM 181 can be configured to provide stability control in the form of straight line tracking, wheel slip and traction control, hillside stability and rollover protection. The SCM 181 may include some or all of the features and functionality described in commonly owned U.S. Pat. No. 9,764,734, the terms of which are incorporated herein by reference in its entirety. For example, the SCM 181 may be an Inertial Measurement Unit (IMU) module configured to include a 9-axis or 11-axis IMU incorporating an accelerometer, gyroscope and magnetometer. The IMU module may also include a microprocessor, temperature sensor, CAN interface and other elements.

FIG. 11 illustrates certain component relationships and the basic control configuration of the drive assemblies. The relationship between the drive assemblies and electrical power supply components (battery 175 and alternator 176) is also indicated, as is the connection between the drive assemblies and the CAN Bus 160. It should be noted that alternator 176 may be any type of suitable electrical power generator.

FIG. 12 depicts an electric actuator 230 of the present disclosure and adaptive components for mounting the electric actuator 230 on a hydraulic pump 271 to form a pump assembly 270 that is controlled via electric actuator 230. Electric actuator 230 is essentially the same as electric actuator 30 described previously herein. The basic construction of hydraulic pump 271 is known in the art, and is disclosed in commonly-owned U.S. Pat. No. 6,332,393, the terms of which are incorporated herein by reference in their entirety. Hydraulic pump 271 comprises an input shaft 274 and a main housing 272 having an end cap 273 mounted thereon. End cap 273 can be rotated 180 degrees about the rotational axis 274Ax of input shaft 274 to enable configuration of the left hand and right hand pump assemblies 270L, 270R shown in FIG. 13.

When hydraulic pump 271 is assembled, the drive interface between electric actuator 230 and hydraulic pump 271 is similar to that shown in FIG. 3. Trunnion arm 227 comprises a control shaft 227 a having an adapter mounting interface 227 b formed thereon to receive a drive adapter 211. Drive adapter 211 includes a plurality of projections 211 a and a clocked alignment projection 211 b that serve the same function as the previously described projections 11 a, 11 b of drive adapter 11. Drive adapter 211 also has a mounting interface 211 c similar to mounting interface 11 c. Drive adapter 211 differs from drive adapter 11 due to an O-ring 214 installed thereon. O-ring 214 rotates against a sealing face 215 a formed on a sealing adapter 215. O-ring 214 cooperates with a seal 216 installed on the sealing adapter 215 to seal electric actuator 230 when electric actuator 230 is attached to a mounting adapter 210. Similar to fastener 12 and magnet 13 described previously herein, a specialized fastener 212 with a cylindrical diametric magnet 213 secured thereto engages a threaded bore 227 c formed in the control shaft 227 a to attach the drive adapter 211 following attachment of the mounting adapter 210 to main housing 272. Mounting adapter 210 is interposed between main housing 272 and adapter 211 and is secured to main housing 272 by means of a single fastener 217 that is installed through one of two countersunk openings 210 c to engage a threaded bore 272 b formed in main housing 272. Although just one countersunk opening 210 c is required to mount the mounting adapter 210, two countersunk openings 210 c can be provided to accommodate different pump models and/or to allow 180 degree rotation of electric actuator 230 about axis 227Ax in order to provide an optional mounting orientation in relation to hydraulic pump 271 (or other similar hydraulic pump configuration). Mounting adapter 210 comprises a clearance opening 210 a that allows the control shaft 227 a to protrude therethrough to engage adapter 211 and has four anti-rotation projections or tabs 210 b (two of which are formed on each of its inboard and outboard faces) to engage pilot opening 272 a and a similar opening in electric actuator 230. The two projections or tabs 210 b formed on the outboard face of mounting adapter 210 are shown in FIG. 12. These two tabs 210 b may be similar in form or may differ compared to the two projections or tabs 210 b formed on the inboard face of mounting adapter 210, but they serve the same basic function of preventing rotation of a component or assembly that is secured using a single fastener. Referring again to FIG. 3, gasket seal 37 of electric actuator 30 is deleted from the “similar opening in electric actuator 230” and replaced by the sealing adapter 215 and seal 216. The two outboard tabs 210 b interface with anti-rotation tabs in electric actuator 230 that are equivalent to the anti-rotation tabs 31 a shown in FIG. 3 and overlap the sealing adapter 215 to aid in positioning sealing adapter 215 while preventing rotation of electric actuator 230 about the axis 225Ax of fastener 225. Fastener 225 engages threaded bore 210 e formed in boss 210 d to attach electric actuator 230 to mounting adapter 210.

FIG. 13 depicts a zero turn vehicle 290 that is similar to vehicle 190 in many respects, including use of a vehicle control system 280 that is substantially the same as the previously described vehicle control system 180. Vehicle 290 includes a prime mover, such as internal combustion engine 291, that drives a pair of pump assemblies 270L, 270R by means of a conventional power transfer apparatus, such as belt and pulley system 297. Each pump assembly 270L, 270R is functionally the same as the previously described pump assembly 270, and pump assembly 270R is essentially a mirror image of pump assembly 270L. The output of pump assemblies 270L, 270R is controlled by electric actuators 230L, 230R, respectively. Each electric actuator 230L, 230R is functionally the same as the previously described electric actuator 230, and electric actuator 230R is essentially a mirror image of electric actuator 230L. Electric actuators 230L, 230R are connected to a VIM 261 by way of a CAN Bus 260. The VIM 261 and the CAN Bus 260 are very similar to the previously described VIM 161 and CAN Bus 160, though there may be some relatively minor differences in firmware, software, and number of connections to CAN Bus 260.

Hydraulic lines 296 connect the pump assemblies 270L, 270R to hydraulic wheel motors 294L, 295R, respectively. (Only the basic hydraulic fluid supply lines are shown schematically since similar pump and wheel motor arrangements are well known in the art. This drive arrangement may also include a hydraulic fluid reservoir and associated hydraulic lines, for example.) Each of the hydraulic wheel motors 294L, 295R includes an output axle 279 engaged to a drive wheel 293 to provide propulsion and steering as directed by the vehicle operator via control levers 183L, 183R engaged to respective speed control mechanisms 165L, 165R or via optional joysticks 299L, 299R, each comprising a Joystick Control Module (JSM), or via a single joystick as described previously herein. Joysticks 299L, 299R may be configured with a limited range of motion (such as forward and reverse movement only) so that they function in a manner similar to control levers 183L, 183R and are each biased to return to a neutral position.

FIGS. 14 and 15 depict an electric actuator 30 described previously herein and alternative adaptive components for mounting the electric actuator 30 on a hydraulic pump 371 to form a pump assembly 370 that includes control by electric actuator 30. The hydraulic pump 371 may be the same as hydraulic pump 271 with the exception of the adapter mounting interface as will be described below.

In pump assembly 370, the adapter mounting interface 227 b of trunnion arm 227 receives a drive adapter 311 with a mounting adapter 310 disposed between the pump main housing 372 and the drive adapter 311. Mounting adapter 310 includes a stop surface 310 f to limit axial motion of drive adapter 311 toward main housing 372. Drive adapter 311 includes a plurality of projections 311 a and a clocked alignment projection 311 b that serve the same function as the previously described projections 11 a, 11 b of drive adapter 11. Drive adapter 311 also has a mounting interface 311 c similar to mounting interface 11 c. Similar to pump assembly 270, a specialized fastener 212 with a cylindrical diametric magnet 213 secured thereto engages a threaded bore 227 c formed in the control shaft 227 a to attach the drive adapter 311 following attachment of the mounting adapter 310 to main housing 372. Mounting adapter 310 is secured to main housing 372 by means of a single fastener 317 that is installed through a countersunk opening 310 c to engage a threaded bore 372 b formed in main housing 372. Mounting adapter 310 comprises a clearance opening 310 a that allows the control shaft 227 a to protrude therethrough to engage adapter 311 and has a pilot projection 310 g formed concentrically about clearance opening 310 a to engage pilot opening 372 a. This engagement prevents rotation of adapter 310 about the longitudinal axis 317Ax of fastener 317. An O-ring 318 is positioned in an O-ring groove 310 h formed concentrically about the pilot projection 310 g, as shown in FIG. 15, and O-ring 318 seals the adapter 310 against a flat seal land 372 c machined about the pilot opening 372 a. A seal pressure ring 310 b formed on the opposite side of the mounting adapter 310 presses against the gasket seal 37 shown in FIG. 3 to seal electric actuator 30 when electric actuator 30 is attached to the mounting adapter 310. The seal pressure ring 310 b also interfaces with the gear housing 31 to prevent rotation of electric actuator 30 about fastener axis 25Ax. The longitudinal axis of magnet 213 is collinear with the rotational axis 227Ax of trunnion arm 227, and is oriented perpendicular to the magnetic field sensor chip 46. Fastener 25 engages threaded bore 310 e formed in boss 310 d to attach electric actuator 30 to the mounting adapter 310.

While specific embodiments have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those presented herein could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any equivalent thereof. 

What is claimed is:
 1. A drive assembly, comprising: a variable drive apparatus disposed in a drive apparatus housing, the variable drive apparatus comprising a rotatable control shaft having a distal end disposed in the drive apparatus housing and a proximal end external to the drive apparatus housing; an adapter, and a fastener connecting the adapter to the proximal end of the rotatable control shaft; an electric actuator disposed adjacent to the drive apparatus housing, the electric actuator comprising: an electric motor; an actuator housing into which the proximal end of the rotatable control shaft extends; a magnetic field sensor disposed in the actuator housing; and a gear train configured to be driven by the electric motor and having a plurality of gears, wherein one of the plurality of gears is engaged to and rotates the adapter; and a cylindrical diametric magnet disposed in the fastener to position the magnet adjacent to the magnetic field sensor within the actuator housing.
 2. The drive assembly of claim 1, wherein the magnet is disposed in a bore formed in the fastener.
 3. The drive assembly of claim 1, wherein the variable drive apparatus comprises a swash plate engaged to and controlling an output of a variable displacement pump, wherein the rotatable control shaft is formed as part of the swash plate.
 4. The drive assembly of claim 3, wherein the magnet is disposed in a bore formed in the fastener.
 5. A drive assembly, comprising: a variable drive apparatus disposed in a drive apparatus housing, the variable drive apparatus comprising a rotatable control shaft having a distal end disposed in the drive apparatus housing and a proximal end external to the drive apparatus housing; and an electric actuator comprising: a gear housing comprising a first side mounted adjacent to the drive apparatus housing and a second side opposite thereto, the gear housing further comprising an electric motor end cap integrally formed as a part of the gear housing; a gear train disposed in the gear housing and comprising a plurality of gears; a jack shaft comprising a first end on which at least one of the plurality of gears is disposed and a second end threadably connected to the drive apparatus housing; an electrical housing secured to the second side of the gear housing, wherein the proximal end of the rotatable control shaft extends through the gear housing and into the electrical housing; an electric circuit disposed in the electrical housing; a motor housing secured to the electric motor end cap; and an electric motor having a motor output shaft extending out of the motor housing.
 6. The drive assembly of claim 5, wherein the electric actuator is threadably connected to the drive apparatus housing by only the jack shaft.
 7. The drive assembly of claim 6, further comprising a pilot for aligning the gear housing onto the drive apparatus housing to facilitate the jack shaft in securely attaching the electric actuator to the drive apparatus housing.
 8. The drive assembly of claim 5, wherein the jack shaft further comprises an integral thrust washer disposed between the first end and the second end, the integral thrust washer providing a bearing surface for the at least one of the plurality of gears disposed on the jack shaft.
 9. The drive assembly of claim 8, wherein the integral thrust washer bears against the gear housing of the electric actuator that is attached to the drive apparatus housing.
 10. The drive assembly of claim 5, further comprising a magnet mounted to the proximal end of the rotatable control shaft and a magnetic field sensor disposed in the electrical housing, wherein the magnet is disposed adjacent to the magnetic field sensor.
 11. The drive assembly of claim 10, further comprising an adapter attached to the proximal end of the rotatable control shaft.
 12. The drive assembly of claim 11, further comprising a fastener connecting the adapter to the proximal end of the rotatable control shaft, wherein the magnet is a cylindrical diametric magnet disposed in the fastener.
 13. The drive assembly of claim 12, wherein the magnet is disposed in a bore formed in the fastener.
 14. The drive assembly of claim 11, wherein the plurality of gears of the gear train comprises a sector gear, wherein the adapter is drivingly engaged to the sector gear.
 15. A drive assembly comprising a variable drive apparatus disposed in a drive apparatus housing and having a rotatable control shaft having a distal end disposed in the drive apparatus housing and a proximal end external to the drive apparatus housing, the drive assembly comprising: an actuator assembly comprising a gear housing, an electrical housing secured to the gear housing and an electric motor; a gear train comprising a plurality of gears disposed in the gear housing and an electric circuit disposed in the electrical housing; and a single fastener connecting the actuator assembly to the drive apparatus housing, wherein the single fastener comprises a first end on which at least one of the plurality of gears of the gear train is disposed and a second end having threads and capable of connecting to the drive apparatus housing.
 16. The drive assembly of claim 15, further comprising a magnet mounted to the proximal end of the rotatable control shaft and a magnetic field sensor disposed in the electrical housing, wherein the magnet is disposed adjacent to the magnetic field sensor.
 17. The drive assembly of claim 15, wherein the gear housing comprises a first side mounted adjacent to the drive apparatus housing and a second side opposite thereto, and the electrical housing is secured to the second side of the gear housing. 